Currently, with the increasing popularity of smart phones, it is becoming more and more prevalent to use a phone to take pictures. More particular, certain phone users like to take self-portrait pictures and some of these self-portrait pictures are erotic pictures. As a result, there exist many sensitive pictures in the phone's picture library.
In related art, in order to protect privacy and avoid unsolicited release of the sensitive pictures, the phone users usually need to manually move these sensitive pictures into private albums, which would be hidden and encrypted.